Shallow Depth of Field
A narrow zone of sharpness that isolates the subject against a strongly blurred foreground and background.
Measured in
m
In depth
Shallow depth is produced by some combination of a wide aperture, a long focal length, a close subject and a distant background — and it is the background distance that photographers most often forget. It directs attention forcefully, but it also removes context, so it is a tool of emphasis rather than a default setting.
Examples in practice
An 85 mm lens at f/1.8 with the subject three metres from a hedge reduces the hedge to a wash of green tones.